Ballistic nylon is a thick, tough, nylon fabric with several uses. Ballistic nylon was developed by the DuPont corporation as a material for flak jackets to be worn by World War II airmen. The term ballistic nylon originates in the fabric's intended function, protecting its wearers from flying debris and fragmentation caused by bullet and artillery-shell impacts. It was not effective against most pistol and rifle bullets, let alone heavy 20 mm and 30 mm autocannons, with which Axis fighters often were armed. Ballistic nylon has been replaced by Kevlar and other, more effective, bullet resistant fabrics for these cases.
The original specification for ballistic nylon was an 18 ounce nylon fabric made from 1050 denier high tenacity nylon yarn in a 2×2 basketweave. Today the term is often used to refer to any nylon fabric that is made with a "ballistic weave", typically a 2×2 or 2×3 basketweave. It can be woven from nylon yarns of various denier such as 840 denier and 1680 denier. Denier refers to the weight, not the strength, of the fabric. Laboratory tests have been run and the double weave 1050 denier fabric is the strongest and most durable fabric for its denier weight level. The 1680 denier is a good alternative that has a similar strength but lighter weight than the 1050 as it resists abrasion and tearing. Ballistic nylon is hard to dye, so it is often found in black or similar dark colors.